I've looked at a few different posts on StackOverflow, but didn't really find the one that solved my issue. The code below works, but it's flickering constantly.
Essentially, I'm just creating a starry background where random stars will fade in and out
var canvas = document.querySelector("canvas");
canvas.width = window.innerWidth;
canvas.height = window.innerHeight;
var c = canvas.getContext("2d");
function Star(x, y, a, z, size, b) {
this.x = x;
this.y = y;
this.z = z;
this.a = a;
this.size = size;
this.b = b;
this.draw = function () {
c.fillStyle = "rgba(155, 241, 052, 1)";
c.beginPath();
c.arc(this.x, this.y, this.z, 0, Math.PI * 2, false);
c.fill();
};
this.update = function () {
if (this.z > this.size) {
this.a = 0;
}
if (this.z < 0) {
this.a = 1;
}
if (this.a == 1) {
this.z += this.b;
} else {
this.z -= this.b;
}
this.draw();
};
}
var starArray = [];
for (var i = 0; i < 100; i++) {
var size = Math.random() * 3 + 2; //size range
var x = Math.random() * innerWidth; //x coordinate
var y = Math.random() * innerHeight; //y coordinate
var z = Math.random() * size; //star size
var a = 1; //on-off switch for the star to fade in or fade out
var b = Math.random() / 20; //fade-in/fade-out rate (random for each star)
starArray.push(new Star(x, y, a, z, size, b));
}
function animate() {
requestAnimationFrame(animate);
c.clearRect(0, 0, innerWidth, innerHeight);
for (var i = 0; i < starArray.length; i++) {
starArray[i].update();
}
}
animate();
You are providing a negative radius to CanvasRenderingContext2D.arc(). You may need to rethink your logic or use Math.abs to make sure the radius provided is always non-negative.
c.arc(this.x, this.y, Math.abs(this.z), 0, Math.PI * 2, false);
var canvas = document.querySelector("canvas");
canvas.width = window.innerWidth;
canvas.height = window.innerHeight;
var c = canvas.getContext("2d");
function Star(x, y, a, z, size, b) {
this.x = x;
this.y = y;
this.z = z;
this.a = a;
this.size = size;
this.b = b;
this.draw = function () {
c.fillStyle = "rgba(155, 241, 052, 1)";
c.beginPath();
c.arc(this.x, this.y, Math.abs(this.z), 0, Math.PI * 2, false);
c.fill();
};
this.update = function () {
if (this.z > this.size) {
this.a = 0;
}
if (this.z < 0) {
this.a = 1;
}
if (this.a == 1) {
this.z += this.b;
} else {
this.z -= this.b;
}
this.draw();
};
}
var starArray = [];
for (var i = 0; i < 100; i++) {
var size = Math.random() * 3 + 2; //size range
var x = Math.random() * innerWidth; //x coordinate
var y = Math.random() * innerHeight; //y coordinate
var z = Math.random() * size; //star size
var a = 1; //on-off switch for the star to fade in or fade out
var b = Math.random() / 20; //fade-in/fade-out rate (random for each star)
starArray.push(new Star(x, y, a, z, size, b));
}
function animate() {
requestAnimationFrame(animate);
c.clearRect(0, 0, innerWidth, innerHeight);
for (var i = 0; i < starArray.length; i++) {
starArray[i].update();
}
}
animate();
<canvas></canvas>
You are getting negative radius on the arc call, just do:
c.arc(this.x, this.y, Math.max(this.z, 0), 0, Math.PI * 2, false);
Related
I have a top to bottom falling canvas animation, but I want to reverse it (go from bottom to top). I can't figure out how to change the direction
I have my code here
http://js.do/code/176399
sample:
function Ember(x, y, s /*radius*/ , p /*num points*/ ) {
this.x = x;
this.y = y;
this.s = s;
this.p = p;
this.img = document.createElement('canvas');
var context = this.img.getContext('2d'),
len = this.s / 1.45;
this.img.height = this.img.width = this.s * 2;
context.translate(this.s, this.s);
context.rotate((Math.PI * 1 / 10));
context.beginPath();
for (var i = 0; i < p; i++) {
context.lineTo(0, -s);
context.rotate((Math.PI * 2 / (p * 2)));
context.lineTo(0, s);
context.rotate((Math.PI * 2 / (p * 2)));
}
context.closePath();
context.shadowBlur = this.s / 3;
context.shadowColor = 'rgba(174, 12, 1, 0.9)';
context.fillStyle = 'rgba(133,80,33,.45)';
context.fill();
}
Just need to reverse the "fall" to bottom to top.
Update:
following off of Jared's suggestion
Changed:
embers[i].y += embers[i].vy;
to:
embers[i].y -= embers[i].vy;
However, I only get one animation cycle would like to have it continually animate new embers on the screen
Take a look at this line where you update the ember's Y position:
embers[i].y = -embers[i].s;
Try changing this to something like this:
embers[i].y = embers[i].s;
<canvas id="canvas"></canvas>
<script>
function Ember(x, y, s /*radius*/ , p /*num points*/ ) {
this.x = x;
this.y = y;
this.s = s;
this.p = p;
this.img = document.createElement('canvas');
var context = this.img.getContext('2d'),
len = this.s / 1.45;
this.img.height = this.img.width = this.s * 2;
context.translate(this.s, this.s);
context.rotate((Math.PI * 1 / 10));
context.beginPath();
for (var i = 0; i < p; i++) {
context.lineTo(0, -s);
context.rotate((Math.PI * 2 / (p * 2)));
context.lineTo(0, s);
context.rotate((Math.PI * 2 / (p * 2)));
}
context.closePath();
context.shadowBlur = this.s / 3;
context.shadowColor = 'rgba(174, 12, 1, 0.9)';
context.fillStyle = 'rgba(133,80,33,.45)';
context.fill();
}
window.requestAnimationFrame = (function () {
return window.requestAnimationFrame ||
window.webkitRequestAnimationFrame ||
window.mozRequestAnimationFrame ||
function (callback) {
window.setTimeout(callback, 1000 / 60);
};
})();
var canvas, context, height, width, embers;
setTimeout(init, 10);
function init() {
canvas = document.getElementById('canvas');
context = canvas.getContext('2d');
height = canvas.height = document.body.offsetHeight;
width = canvas.width = document.body.offsetWidth;
embers = [];
for (var i = 0; i < 150; i++) {
var x = Math.random() * width,
y = Math.random() * height,
s = Math.random() * 5 + 5,
p = Math.random() * 8 + 8;
var s = new Ember(x, y, s, p);
s.vx = Math.random() * 2 - 1;
s.vy = Math.random() * 2 + 1;
s.r = Math.random() * 360;
embers.push(s);
}
update();
render();
}
function update() {
for (var i = 0, l = embers.length; i < l; i++) {
embers[i].r += embers[i].vx / 10;
embers[i].x += embers[i].vx;
embers[i].y -= embers[i].vy;
if (embers[i].y < 0) {
embers[i].y = Math.random()*height;
embers[i].vx = Math.random() * 2 - 1;
embers[i].vy = Math.random() * 2 + 1;
}
}
setTimeout(update, 1000 / 30);
}
function render() {
context.clearRect(0, 0, width, height);
for (var i = 0, l = embers.length; i < l; i++) {
context.save();
context.translate(embers[i].x, embers[i].y);
context.rotate(embers[i].r);
context.drawImage(embers[i].img, 0, 0);
context.restore();
}
requestAnimationFrame(render);
}
</script>
Wrong if condition in update function, change it to check if v(embers[i].y < 0), ans set appropriate new y position
if (embers[i].y < 0) {
embers[i].y = Math.random()*height;
I have the following canvas. I want it so that when the user clicks the canvas, I will go to google.com, and I want to keep the button element. This is my code:
//set the variables
var a = document.getElementById('canvas'),
c = a.getContext('2d'),
a.style.width = '200px';
a.style.height = '50px';
area = w * h,
particleNum = 300,
ANIMATION;
var particles = [];
//create the particles
function Particle(i) {
this.id = i;
this.hue = rand(50, 0, 1);
this.active = false;
}
Particle.prototype.build = function() {
this.x = w / 2;
this.y = h / 2;
this.r = rand(7, 2, 1);
this.vx = Math.random() * 10 - 5;
this.vy = Math.random() * 10 - 5;
this.gravity = .01;
this.opacity = Math.random() + .5;
this.active = true;
c.beginPath();
c.arc(this.x, this.y, this.r, 0, 2 * Math.PI, false);
c.fillStyle = "hsla(" + this.hue + ",100%,50%,1)";
c.fill();
};
Particle.prototype.draw = function() {
this.active = true;
this.x += this.vx;
this.y += this.vy;
this.vy += this.gravity;
this.hue -= 0.5;
this.r = Math.abs(this.r - .05);
c.beginPath();
c.arc(this.x, this.y, this.r, 0, 2 * Math.PI, false);
c.fillStyle = "hsla(" + this.hue + ",100%,50%,1)";
c.fill();
// reset particle
if(this.r <= .05) {
this.active = false;
}
};
//functionality
function drawScene() {
c.fillStyle = "black";
c.fillRect(0,0,w,h);
for(var i = 0; i < particles.length; i++) {
if(particles[i].active === true) {
particles[i].draw();
} else {
particles[i].build();
}
}
ANIMATION = requestAnimationFrame(drawScene);
}
function initCanvas() {
var s = getComputedStyle(a);
if(particles.length) {
particles = [];
cancelAnimationFrame(ANIMATION);
ANIMATION;
console.log(ANIMATION);
}
w = a.width = window.innerWidth;
h = a.height = window.innerHeight;
for(var i = 0; i < particleNum; i++) {
particles.push(new Particle(i));
}
drawScene();
console.log(ANIMATION);
}
//init
(function() {
initCanvas();
addEventListener('resize', initCanvas, false);
})();
//helper functions
function rand(max, min, _int) {
var max = (max === 0 || max)?max:1,
min = min || 0,
gen = min + (max - min) * Math.random();
return (_int) ? Math.round(gen) : gen;
};
#canvas{
width: 200;
height: 50;
}
<div class="wrapper">
<a href="index.html">
<button align=center onclick="handleClick()">
<canvas width="200" height="50" id="canvas" align=center></canvas>
<span class="text">SUBMIT</span>
</button>
</a>
</div>
Although, I only see the button, and no the canvas. How can I fix this?
You got a lot of errors actually buddy (variable declaration is the biggest problem) but by following the errors will give you a way to fix it, I don't know if this is the fix you want.
//set the variables
var a = document.getElementById('canvas'),
c = a.getContext('2d');
a.style.width = '200px';
a.style.height = '50px';
var w, h;
var area = w * h,
particleNum = 300,
ANIMATION;
var particles = [];
//create the particles
function Particle(i) {
this.id = i;
this.hue = rand(50, 0, 1);
this.active = false;
}
Particle.prototype.build = function() {
this.x = w / 2;
this.y = h / 2;
this.r = rand(7, 2, 1);
this.vx = Math.random() * 10 - 5;
this.vy = Math.random() * 10 - 5;
this.gravity = 0.01;
this.opacity = Math.random() + .5;
this.active = true;
c.beginPath();
c.arc(this.x, this.y, this.r, 0, 2 * Math.PI, false);
c.fillStyle = "hsla(" + this.hue + ",100%,50%,1)";
c.fill();
};
Particle.prototype.draw = function() {
this.active = true;
this.x += this.vx;
this.y += this.vy;
this.vy += this.gravity;
this.hue -= 0.5;
this.r = Math.abs(this.r - 0.05);
c.beginPath();
c.arc(this.x, this.y, this.r, 0, 2 * Math.PI, false);
c.fillStyle = "hsla(" + this.hue + ",100%,50%,1)";
c.fill();
// reset particle
if (this.r <= 0.05) {
this.active = false;
}
};
//functionality
function drawScene() {
c.fillStyle = "black";
c.fillRect(0, 0, w, h);
for (var i = 0; i < particles.length; i++) {
if (particles[i].active === true) {
particles[i].draw();
} else {
particles[i].build();
}
}
ANIMATION = requestAnimationFrame(drawScene);
}
function initCanvas() {
var s = getComputedStyle(a);
if (particles.length) {
particles = [];
cancelAnimationFrame(ANIMATION);
ANIMATION;
console.log(ANIMATION);
}
w = a.width = window.innerWidth;
h = a.height = window.innerHeight;
for (var i = 0; i < particleNum; i++) {
particles.push(new Particle(i));
}
drawScene();
console.log(ANIMATION);
}
//init
(function() {
initCanvas();
addEventListener('resize', initCanvas, false);
})();
//helper functions
function rand(max, min, _int) {
var max = (max === 0 || max) ? max : 1,
min = min || 0,
gen = min + (max - min) * Math.random();
return (_int) ? Math.round(gen) : gen;
};
#canvas {
width: 200px;
height: 50px;
}
<div class="wrapper">
<a href="index.html">
<button align=center onclick="handleClick()">
<canvas width="200" height="50" id="canvas" align=center> </canvas>
<span class="text">SUBMIT</span>
</button>
</a>
</div>
I have the following canvas. I'm trying to make it smaller using the width and height attributes, but it doesn't work. This is my code:
<!DOCTYPE HTML>
<html>
<head>
<style>
body {
margin: 0px;
padding: 0px;
}
</style>
</head>
<body>
<canvas id="canvas" width="200" height="50"></canvas>
<script>
//set the variables
var a = document.getElementById('canvas'),
c = a.getContext('2d'),
w = a.width = window.innerWidth,
h = a.height = window.innerHeight,
area = w * h,
particleNum = 300,
ANIMATION;
var particles = [];
//create the particles
function Particle(i) {
this.id = i;
this.hue = rand(50, 0, 1);
this.active = false;
}
Particle.prototype.build = function() {
this.x = w / 2;
this.y = h / 2;
this.r = rand(7, 2, 1);
this.vx = Math.random() * 10 - 5;
this.vy = Math.random() * 10 - 5;
this.gravity = .01;
this.opacity = Math.random() + .5;
this.active = true;
c.beginPath();
c.arc(this.x, this.y, this.r, 0, 2 * Math.PI, false);
c.fillStyle = "hsla(" + this.hue + ",100%,50%,1)";
c.fill();
};
Particle.prototype.draw = function() {
this.active = true;
this.x += this.vx;
this.y += this.vy;
this.vy += this.gravity;
this.hue -= 0.5;
this.r = Math.abs(this.r - .05);
c.beginPath();
c.arc(this.x, this.y, this.r, 0, 2 * Math.PI, false);
c.fillStyle = "hsla(" + this.hue + ",100%,50%,1)";
c.fill();
// reset particle
if(this.r <= .05) {
this.active = false;
}
};
//functionality
function drawScene() {
c.fillStyle = "black";
c.fillRect(0,0,w,h);
for(var i = 0; i < particles.length; i++) {
if(particles[i].active === true) {
particles[i].draw();
} else {
particles[i].build();
}
}
ANIMATION = requestAnimationFrame(drawScene);
}
function initCanvas() {
var s = getComputedStyle(a);
if(particles.length) {
particles = [];
cancelAnimationFrame(ANIMATION);
ANIMATION;
console.log(ANIMATION);
}
w = a.width = window.innerWidth;
h = a.height = window.innerHeight;
for(var i = 0; i < particleNum; i++) {
particles.push(new Particle(i));
}
drawScene();
console.log(ANIMATION);
}
//init
(function() {
initCanvas();
addEventListener('resize', initCanvas, false);
})();
//helper functions
function rand(max, min, _int) {
var max = (max === 0 || max)?max:1,
min = min || 0,
gen = min + (max - min) * Math.random();
return (_int) ? Math.round(gen) : gen;
};
</script>
</body>
</html>
Pay more attention here:
var a = document.getElementById('canvas'),
c = a.getContext('2d'),
w = a.width = window.innerWidth,
h = a.height = window.innerHeight,
area = w * h,
As you can see, w is the width of the window and h is the height of the window. Try to edit w and h variable with custom values and tell me if it worked ;)
EDIT:
Simply replace h and w with this in your script tag:
a.style.width = '500px'; //random value, insert custom here
a.style.height = '500px';
I want to make the particles follow the mouse and I am not sure on how to do that.
I figured I can replace the x and y with the mouses position but I can figure that out either.
I would appreciate an almost exact answer and not examples please.
window.onload = function() {
var canvas = document.createElement("canvas"),
c = canvas.getContext("2d"),
particles = {}
particleIndex = 0,
particleNum = Math.random() * 2;
canvas.width = 400;
canvas.height = 400;
document.body.appendChild(canvas);
c.fillStyle = "black";
c.fillRect(0, 0, canvas.width, canvas.height);
function Particle() {
this.x = canvas.width / 10;
this.y = canvas.height / 2;
this.vx = Math.random() * 10 - 5;
this.vy = Math.random() * 10 - 5;
this.gravity = .2;
particleIndex++;
particles[particleIndex] = this;
this.id = particleIndex;
this.life = 0;
this.maxLife = Math.random() * 30 + 10;
this.color = "rgb(" + parseInt(Math.random() * 255, 10) + ",0,0)";
this.color2 = "hsl(" + parseInt(Math.random() * 255, 10) + ",50%,50%)";
}
Particle.prototype.draw = function() {
this.x += this.vx;
this.y += this.vy;
if (Math.random() < 0.1) {
this.vx = Math.random() * 10 - 5;
this.vy = Math.random() * 10 - 5;
}
this.vy += this.gravity;
this.life++;
if (this.Life >= this.maxLife) {
delete particles[this.id];
}
c.fillStyle = this.color2;
c.fillRect(this.x, this.y, 10, 10);
};
//var p = new Particle();
setInterval(function() {
c.fillStyle = "rgba(0,0,0,0.5)";
c.fillRect(0, 0, canvas.width, canvas.height);
for (var i in particles) {
particles[i].draw();
}
for (var i = 0; i < particleNum; i++) {
new Particle();
}
}, 30);
};
Been trying to animate an object on canvas by putting it in an array but it wont seem to work.
Only have one object drawn at the moment but the thought is to add several more objects to the canvas hence the array.
Is there something wrong with the functions im using to draw and animate the object?
var draw;
function Canvas(canvas, ctx) {
this.canvas = canvas;
this.ctx = ctx;
}
function Direction(x, y) {
this.x = x;
this.y = y;
}
function Measures(cW, cH, radius, hR, degree, dirX, dirY, degree) {
this.cW = cW;
this.cH = cH;
this.radius = radius;
this.hR = hR;
this.dirX = dirX;
this.dirY = dirY;
this.degree = degree;
}
function Drawing(cW, cH, width, height, radius, hR, color) {
this.cW = canvas.width;
this.cH = canvas.height;
this.width = width;
this.height = height;
this.radius = height / 2;
this.hR = width - this.radius;
this.color = color;
this.render = function() {
ctx.fillStyle = this.color;
ctx.strokeStyle = this.color;
ctx.lineWidth = 1;
ctx.save();
ctx.translate(this.x, this.y);
ctx.rotate(this.degree * Math.PI / 180);
ctx.translate(-this.x, -this.y);
ctx.beginPath();
ctx.moveTo(this.x, this.y);
ctx.lineTo(x + this.hR, this.y);
ctx.arc(this.x + this.hR, this.y + this.radius, this.radius, - Math.PI / 2, Math.PI / 2);
ctx.lineTo(this.x, this.y + height);
ctx.closePath();
ctx.fill();
ctx.stroke();
ctx.restore();
}
this.move = function(multiplier) {
var multiplier = 2;
var borders = 5;
if(this.dirX > 0 && this.x > this.cW - borders - width){
this.degree = 90;
this.dirX = 0;
this.dirY = 1;
this.x = cW - borders;
}
else if(this.dirY > 0 && this.y > this.cH - borders - width){
this.degree = 180;
this.dirX = -1;
this.dirY = 0;
this.y = this.cH - borders;
}
else if(this.dirX < 0 && this.x < borders + width){
this.degree = -90;
this.dirX = 0;
this.dirY = -1;
this.x = borders;
}
else if(this.dirY < 0 && this.y < borders + width){
this.degree = 0;
this.dirX = 1;
this.dirY = 0;
this.y = borders;
}
this.x += this.dirX * multiplier;
this.y += this.dirY * multiplier;
this.render();
}
}
function animate() {
ctx.clearRect(0, 0, this.cW, this.cH);
draw.forEach(function(object) {
object.render(2);
});
requestAnimationFrame(animate);
}
function init() {
this.canvas = document.getElementById("my_canvas");
this.ctx = canvas.getContext("2d");
this.degree = Math.PI / 2;
draw = [];
draw.push(new Drawing(5, 5, 80, 60, new Direction(1,0), "#E5E5E5"));
animate();
}
window.onload = init;
</script>
<canvas id="my_canvas" width="1000" height="800" style="background-color:#33CC33"></canvas>